The immune-enhancing potential of peptide fractions from fermented Spirulina platensis by mixed probiotics

Mixed fermentation with different microorganisms can facilitate fermentation metabolism and increase the low molecular metabolites accumulation, thereby enhancing the bioactive activity. In this study, we evaluated the immune-stimulating activities of Spirulina platensis and different extracts from fermented S. platensis (FS) by mixed probiotics in vitro, by measuring the proliferation and Th1/Th2 immunomodulatory potential on murine primary splenic lymphocytes. The results showed that mixed fermentation enhanced the immunomodulatory activity of S. platensis with higher lymphocyte proliferation compared with non-fermented S. platensis (NFS). Notably, the low molecular weight (<3 kDa) peptide fraction from fermented S. platensis (L-PFS), especially at 40 μg/ml, presented the strongest activity in promoting lymphocytes proliferation and modulating cytokines (IL-2 and IL-10) secretion. Meanwhile, L-PFS enhanced the relative mRNA expression of Th1 cytokine (IFN-γ) and Th2 cytokine (IL-4), along with inhibiting the relative mRNA expression of Th1 cytokines (IL-2 and TNF-α) and Th2 cytokine (IL-10) compared with Concanavalin A-treated lymphocytes. Practical applications: Fermentation with mixed probiotics could effectively improve the bioactive activity of S. platensis. In particular, L-PFS screened from the FS could significantly contribute to the immune-enhancing activity of lymphocytes, promote the Th1/Th2 balance, and provide insights for the investigation of FS as the potential immunomodulatory food products.